American historical accounts of the Revolutionary War usually don't explore whether the revolutionists had reasonable grievances

For what it's worth, I've been in the UK since about age four and everything I learned about the American Revolution took the view that the Americans were basically in the right. I don't know how typical this is, but if it is then one explanation (not the only one but maybe the most plausible) is that actually that's the conclusion most reasonable people would come to when looking at the available evidence, and the most plausible explanation of that is that actually the Americans were (according to typical present-day values) in the right.

crimethink

I don't think this sort of overheated language is helpful. No one is going to put you in prison (or even fine you, or even mock you gently) for thinking that current views of the Enlightenment may be misleadingly positive.

These excessively emotional responses resemble how [...]

Emotional responses are also what one would expect if a thing has (really, truly) been established only with difficulty and much opposition and turned out to be extremely beneficial, and if the person making the response is worried that it's being attacked again.

It is usually best to determine that something is wrong before undertaking to explain the mental pathologies that produce it. (The idea described at the other end of that link is about doing this to beliefs, but I think one can say much the same about attitudes.)

Did our ancestors [...] invent the Enlightenment [...] to manage some kind of terror

This seems like one hell of a leap. There are things other than fear of death that lead people to respond emotionally to things. I already mentioned one above, but there are plenty of unflattering ones if NRx has already made it impossible for you to take seriously the possibility that admirers of "Enlightenment values" might be sincere and sane: for instance, maybe people like David Brin have so much of their personal identity invested in such values that criticism of them feels itself like a personal threat. Or maybe they don't really believe in the Enlightenment any more than you do, but they recognize (as you do) the extent to which present-day Western society is built on it, and fear the consequences if it's overthrown.